In long term evolution (LTE) technology a scheduler is responsible for allocating both uplink (UL) and downlink (DL) resources to mobile user equipment (UE) every transmission time interval (TTI) of a radio frame. A TTI is 1 millisecond in duration. The complexity of scheduling and resource allocation combined with tight TTI constraints on processing prohibits recursive types of processing that would lead to optimal allocation of radio resources.
Resource scheduling may also be constrained based on licensing agreements, hardware constraints or software constraints. When finite resources are available as a pool across a group of cells that are being scheduled, a problem of how best to distribute these resources presents challenges. Iterative solutions to achieve global optimization—that is, optimization of resource allocation over all cells—can find on optimal distribution of resources. But these iterative solutions are too complex and time-consuming to be processed in a TTI.
Simplified pre-scheduling allocation of resources—that is, gross allocation of resources across the cells prior to detailed per user equipment (UE) or per-queue scheduling within each cell individually—can be of relatively low complexity. However, if not done accurately, these methods will result in under-utilization of resources and possibly may also result in priority inversion of scheduling entities between cells.